The typical North American Class 8 Line Haul Truck uses a 6×4 tractor with two drive axles in the tractor rear tandem. Alternately, a 6×2 drive line is used with a single drive axle and a dead tag axle in the rear tandem. The 6×2 system is lighter and has a lower parasitic loss compared to the 6×4 system, but suffers from a deficiency in tractive effort under conditions of reduced tire to ground coefficient since the drive axle and tag axle will have the same Gross Axle Weight Rating (GAWR). Systems have been offered to increase the 6×2 single drive axle tractive effort such as wheel differential locks and service brake based electronic traction control systems. Additionally, 6×2 air suspension systems are available that can automatically shift load from the tag axle to the drive axle under conditions of low traction to improve the tractive effort of the drive axle but these systems are slow acting, costly and cumbersome.
In view of the foregoing disadvantages of the prior art, it would be advantageous to have a low cost system that is fast acting, cost effective and easy to incorporate that can safely and effectively improve the 6×2 drive axle traction.